This invention relates to an optical communication network system that uses wavelength division multiplexing.
In general, it is known that optical network systems communicate by wavelength division multiplexing. A conventional optical network system comprises first through N-th communication devices each of which is operable as a reception and transmission device. The first through N-th communication devices are connected to one another by at least one optical multi/demultiplexing device. When each of the first through N-th communication devices is operable as the transmission device, the first through the N-th communication devices produce first through N-th optical signals having first through N-th wavelengths, respectively, where N represents a positive integer greater than two.
It will be assumed that an n-th communication device is operable as the reception device, where n is a variable between one and N, both inclusive. From the optical multi/demultiplexing device, the n-th communication device is supplied with remaining optical signals except for an n-th optical signal as will be described later. The n-th communication device selects a selected one of the remaining optical signals that is produced by a transmission communication device which communicates with the n-th communication device.
As described above, the n-th communication device is supplied with the remaining optical signals to select the selected optical signal from the remaining optical signals when the n-th communication device is operable as the reception device. Accordingly, the n-th communication device has a complex structure inasmuch as the n-th communication device must select the selected optical signal from the remaining optical signals. In other words, it is difficult to construct an optical network system comprising a plurality of communication devices each of which has a simple structure.